The practice of catching fish has existed for millennia. Over the years, both man and beast have advanced the art by adopting numerous methods for making fishing easier and more efficient. The art of modern lure making dates back to the 1920s. Most man-made baits from this era consist of wooden objects with rudimentary mechanical action. The simple Dowagiac line of casting baits produced by Heddon typify the lures of this time period with a buoyant wooden body draped in metallic fishhooks. More recently, the adoption of hard—then soft—plastics as primary lure materials catalyzed an innovative new class of lures known as swimbaits. The first swimbaits where made by the likes of Allen Cole, the Godfather of swimbaits, in Southern California during the mid 1990s. Early models, such as Cole's AC Plug, revolutionized freshwater trophy fishing by adopting modified versions of big sea plastic baits. The AC Plug combines a wooden body with a soft flexible tail to imitate the swimming motion of actual fish and quickly became notorious for catching big game fish. In the quarter century since their introduction, swimbaits have continued to develop with American firms like Pradco and Strike King competing against International firms like Japanese Lucky Craft for control of the international lure market.
In the new millennium, demand for condition optimized fishing lures is flourishing. As fishermen become more aware of the effects water temperature and turbidity, climate, geography, and fish species have on lure performance, they seek custom lures optimized to perform in particular conditions. To meet demand, craftsman in the emerging bespoke art of lure making carefully machine lures that use the principles of drag and resistance to create swimbaits with distinct behavior if pulled through water at a sufficient flow velocity. Embodiments of this art may be comprised of modular body and tail portions that may be optimized to create a shape and motion designed to attract a particular species of fish under certain climate and water conditions.
Many of the same aerodynamic principles used in the aerospace industry influence the hydrodynamic properties of swim baits. These principles include resistance, drag, form drag, interference drag, skin friction, and Reynolds number. Drag, or resistance, is a force acting on solid bodies moving through air or water. The total drag force can be divided into several different components including form drag, interference drag, and skin friction. Form drag is caused by exposure of frontal and leading side areas of an object to flowing fluid. This drag component is influenced by the shape of an object, and is the reason streamlining increases efficiency and speed. Interference drag is caused by interference of fluid flow between adjacent parts of an object, for example the intersection of the tail neck and tail forks. In aviation, interference drag is common at the intersection of the wing and tail sections with the fuselage. In this case, fairings are used to streamline these intersections and decrease interference drag. In the context of fishing lures, interference drag can be created by appendages extending from the fish lure body at steep angles. At high flow velocities, interference drag can help spawn vortices, eddies, and areas of turbulent flow capable of influencing lure movement in the water. Skin friction drag is caused by fluid passing over the surface of an object and increases considerably if the object's surfaces are rough or dirty. Surface friction constitutes two-thirds of an object's total thus, the total force ‘F’ is made up of two components: (i) surface friction: 2πμdu and (ii) form drag: πμdu.
In addition to drag and resistance caused by the shape of an object, the object's motion in a fluid is characterized by the fluid flowing over the object. Reynolds number, Re, represents the relationship between the fluid and the object and is equal to udρ/μ in which ‘ρ’ is the density of the fluid, ‘μ’ is the viscosity of the fluid, ‘d’ is the diameter of the object and ‘u’ is the velocity of the fluid relative to the particle. At high Reynolds numbers—usually at high flow velocities when the fluid is water—the boundary layer between the object and the flowing liquid can separate creating vortices and eddies. As velocity increases, the size of the generated vortices also increases. At Reynolds Numbers greater than 20, flow separation occurs with the formation of vortices in the wake of the object. At Re values between 100 and 200, instabilities in the flow give rise to vortex shedding.
Under the principles outlined above, the motion of swimbait lures depends primarily on the shape of the lure body, the texture of the lure's surface, and the velocity at which the lure travels through water. In addition to the effect of vortices, eddies, and turbulent flow on the lure, the tendency of swim baits to exhibit more movement at higher flow velocities can be explained by Bernoulli's principle—a concept from aerodynamics explaining the lift of an airplane wing. Bernoulli's equation relates an increase in flow velocity to a decrease in pressure and vice versa. Accordingly, at higher flow velocities lures are less constrained by the pressure of water flowing past their surfaces and therefore freer to move about. For this reason, most swimbaits are effective only at a range of elevated flow velocities limiting the use of this type of lure. One of the primary objects of this invention is to create a novel fishing lure that overcomes this flow velocity limitation by retaining swimbait like motion when fished at low velocities—or jigged—and when fished in cold conditions where the lure material is stiffer and sink rates slower.